Crimping tools form, bend, and crimp workpieces such as terminals or eyelets onto the ends of wire cores forming crimped assemblies. In mass production such tools may be mounted on presses that bring the tools to bear against the workpieces. Some crimping tools are configured to crimp terminals or eyelets into circular or semi-circular shapes around an insulation jacket or a fiber optic cable. However, although the workpieces are crimped or formed into circular or semi-circular shapes, the press motion and therefore the tooling motion that forms such arcuate shapes is directed linearly along a single axis. In other words, and as shown in FIGS. 1 and 2, prior art crimping tools engage the terminals or eyelets along a single axis--the press motion axis.
This linear uniaxial motion occurs between plate and anvil portions of a crimping tool as shown in FIGS. 1 and 2. The press imparts motion to the assembly by lowering the plate toward the anvil.
It is difficult to design such a linear motion press-driven crimping system to reliably produce large numbers of uniformly circular crimps. The interrelating geometries of each plate, anvil and workpiece must be designed to close each workpiece together into its final arcuate configuration in response to a single linear motion of the plate. The final crimped configuration of a workpiece must be achieved by shaping the plate and/or anvil to complement the desired arcuate workpiece geometry at the end of the press stroke where the tooling is fully closed, i.e. where the plate is closest to the anvil. Therefore, the tooling geometry in such a system is significantly different from that of the unformed, uncrimped workpiece as shown in FIG. 1. As a result, until the tooling reaches the end of the press stroke, it will exert pressure primarily if not exclusively on the ends of open "arms" of a workpiece until the arms have been forced into their final arcuate configuration. This concentration of pressure can dislodge or distort the terminals during the crimping stroke. The pressure concentration can also cause one "arm" of an open workpiece to close before the other arm resulting in an undesirable overlap.
The use of a linear motion press-driven crimping system can also result in non-uniform stresses existing within the geometries of the crimped assemblies--particularly between the workpieces and cores they are crimped on. Intimate contact with uniform stress between workpiece and core is difficult to achieve with this type of system.
Crimped assemblies are sometimes subjected to pull testing to determine the amount of stress induced by such pulling action within the crimped assembly. Especially when dealing with a core of fiber optic cable, it is very important to achieve the lowest possible level of induced stresses at a specified pull force value. Even stress distribution obviously helps reduce the level of induced stress at any single point around the interface between a workpiece and a core in a crimped assembly. The uniformity of these stresses may become even more important when data transmission rates increase to the point where non-uniformity actually diminishes data transmission rate capability of a fiber optic cable.
An example of a linear motion press-driven crimping system is disclosed in U.S. Pat. No. 5,500,999 issued Mar. 26, 1996 to Yagi et al. and shown in FIGS. 1 and 2. As shown in FIGS. 1 and 2, the Yagi et al. patent describes a terminal crimping device that includes an upper plate or die 100 and a lower plate or anvil 102. An open terminal 104 is placed on the lower plate 102 and a wire core 106 is placed in the open terminal 104 with open arms of the terminal extending upward and outward from either side of the wire core 106. The upper plate 100 is pushed downward in vertical alignment with the lower plate 102, bending the open terminal arms inwardly in such a manner as to form a semi-circular arcuate shape around the wire core, embracing and "biting" into the wire. The upper plate 100 includes curved walls 108 that cause the ends of the terminal arms to slide inward as a press (not shown) forces the upper plate 100 linearly downward toward the lower plate 102. As the ends of the terminal arms meet toward the end of the press cycle, the curved walls 108 impart the final arcuate shape to the arms as it forces the arms into their final crimped position.
What is needed is a crimping apparatus that can crimp a workpiece into an arcuate configuration on a core without requiring multiple press cycles or additional tooling parts such as miniature cams and slides. What is also needed is such an apparatus that gives an operator greater control over the location of stresses that are generated between the workpiece and core of a crimped assembly. Still further, a crimping apparatus is needed that is easy to manufacture and can be mounted on existing presses.